The present invention relates to improvements to Doppler radar systems, and is particularly, but not exclusively, suitable for use with frequency scanning radar systems.
Radar systems are used to detect the presence of objects and to measure the location and movement of objects. It is common for such radar systems to sweep across a given region, scanning the region for the presence of such objects. In order to sweep over the region the radar systems either employ mechanical devices comprising an antenna that physically moves in space, or electronic devices comprising elements that are arranged to steer radiation as it is transmitted and/or received. One known group of such electronic devices is frequency scanning arrays, which, in response to input signals of varying frequencies, can steer a beam in an angular plane. Radar systems can also employ frequency scanning arrays for detection avoidance and/or in the presence of other radar systems and/or to counteract frequency jamming equipment (e.g. by hopping between operating frequencies in order to avoid detection of, interference with, or jamming of, the radar system).
Radar systems are commonly used to identify the Doppler frequency of targets so as to identify the magnitude and direction of movement thereof. In view of the fact that a target's Doppler frequency is dependent on the radar's carrier frequency, the use of frequency scanning antennas in a radar system presents problems in relation to the processing and interpretation of received signals.